The proposed research deals with a) labelling the transport sites for the tubular secretion of organic anions, and b) the effect of toxic chemical on renal functions. In the first study, DIDS (4,4'-disothiocyano-2,'-disulfonic acid stilbene) and NAP-taurine (N-(4-azido-2-nitrophenyl)-2-amino ethyl sulfonate) will be used. The effects of these compounds on the renal transport of organic anions and cations will be made in order to establish the specificity of the effect. The renal transport of these compounds per se will then be studied in the rabbit or rat kidney cortical slice and the isolated, perfused rat kidney. If these compounds are found to interact co-valently with the transport sites in the membrane, attempts will be made to identify the labelled proteins by using an SDS-gel electrophoresis. In the second study, the effects of 2,4,5-trichlorophenoxyacetate (2,4,5-T) and bis (p-chlorophenyl) acetic acid (DDA) on renal functions will be explored using kidney cortical slices, isolated perfused rat kidneys, and in vivo kidneys. Specifically, the mechanisms for renal tubular transport of these compounds as well as the toxic dosage for nephrotoxicity will be investigated.